Speaking before 100 University staff members. Dean of the Faculty Henry Rosovsky yesterday called faculty hiring Harvard's biggest challenge of the decade.

Rosovsky speech was the third in a four lecture series intended to unify the academic and non-academic portions of the faculty. Douglas W. Renick Manager of Training and Development in the University Personnel Office, said yesterday. Presidents Bok and Horner gave similar addresses in the last two months.

"Faculty selection is our most important job," said Rosovsky. "The reputation of Harvard is determined by its faculty."

The University faces increasing obstacles to faculty hiring, including two-career marriages and competition from other schools, which sometimes offer "superstar salaries" to top professors, Rosovsky said.

The hour-long lecture was informational, as Rosovsky explained Harvard's "tub system" for managerial responsibility and the process by which lectured faculty are selected.

In addition, he responded to charges commonly levelled at the College. Insisting that full professors do indeed teach undergraduate courses, that the teaching fellows are qualified, and that the problem of crowding is no worse than at other schools.

Lastly, Rosovsky stressed the importance of Harvard's graduate schools. "They are a necessary condition of our existence," he said, because "the Faculty are drawn by the quality of the graduate student. This is the main focus of the University."

Most of the stall members interviewed afterward said they found the lecture worth while.

"I did not know much about the functions of the Faculty of Arts and Sciences," said Carol I Ishimoto. Head of the Cataloguing and Processing Department of the Harvard College Library. "The program was very in formative," She added.

But another librarian at the lecture who identified himself only as a Harvard graduate said Rosovsky "revealed nothing I did not enjoy the speech much.

The last lecture in the four-part series entitled Harvard and Radelitle in the 80s' will be gives next month by Thomas O'Brien. It nancial vice president. The lecture series is sponsored by the Harvard Managers Ex-change, an administrative group formed in 1977 to encourage interaction between sections of the University.